In the field of photolithography or nanoimprint lithography, a spin coating method is used to form a thin film on a substrate. In the spin coating method, a thin film is formed in an almost uniform thickness by dropping a solution containing film components onto a substrate while rotating the substrate at a certain speed.
However, the resin thickens in the width of several mm at the edge of the substrate due to the surface tension of the dropping solution. The thick resin on the edge of the substrate is called an edge bead.
When a resin film having an edge bead is used for photolithography or nanoimprint lithography, contact between the resin film and a photomask or mold that may be large relative to the substrate becomes insufficient as illustrated in FIG. 6B, thus affecting patterning accuracy.
Japanese Laid-open Patent Publication No. 2006-80298 discloses the step of dropping a photoresist onto a substrate and spin coating the photoresist while rotating the substrate, the step of removing the photoresist from the circumferential edge of the substrate by supplying a solvent to the circumferential edge of the substrate while rotating the substrate, and the step of drying the surface of the photoresist while rotating the substrate.
In Japanese Laid-open Patent Publication No. 6-163389, a polyimide precursor composition at an end of the surface of a semiconductor substrate is removed with a scraper tool and the semiconductor substrate is successively rotated while the polyimide precursor composition is being spin coated on the surface of the substrate.
In Japanese Laid-open Patent Publication No. 2006-80298, since the photoresist is removed from the circumferential edge of the substrate by supplying the solvent, a portion of the photoresist other than at the circumferential edge of the substrate is also removed. Thus, the thickness of the photoresist becomes non-uniform.
In Japanese Laid-open Patent Publication No. 6-163389, the polyimide precursor composition is physically removed with a scraper tool, and therefore the film thickness of the polyimide precursor composition becomes non-uniform.